Dwarves are not heroes?

[William Cloud Hicklin]

It's worth pointing out that in the War of the Last Alliance Dwarves fought on Sauron's side, although those of Durin's Folk did not.

When we turn to the sack of Doriath, we find that while Tolkien had moderated his early view of Dwarves, the actions of those who murdered Thingol and destroyed his kingdom are (in Tolkien's own writings) pretty unambiguously treacherous and wicked (the published version, where Thingol's double-dealing starts it, was an invention by CT/GK). Tolkien in this 'middle period' tried to go with a "Nogrod good, Belegost bad" (or vice-versa) meme: anciently, the "Indrafangs" of Belegost were the Longbeards, and then for a while Nogrod was Khazad-dum, before he decided to remove Thorin's ancestors from Beleriand entirely.

(There is a hint iof evidence, IMO, that during the writing of The Hobbit and the earliest stages of writing the LR, Tolkien envisioned the Misty Mountains as identical to the Ered Luin; there was a subsequent displacemant of the Third Age geography to the eastward.)